Procholecystokinin as Marker of Human Ewing Sarcomas

Abstract

Purpose: Ewing sarcoma is a rapidly growing mesenchymal tumor in young adults. Although it was shown previously to express the cholecystokinin (CCK) gene, it is unknown whether CCK gene expression is detectable at protein level in Ewing sarcoma tumor cell lines, in tumor tissue, and in plasma from Ewing sarcoma patients, and, if so, whether CCK peptides might play a role as tumor markers.Experimental Design: CCK gene expression was evaluated with in situ hybridization or reverse transcription-PCR in tumor tissue. CCK precursors and bioactive CCK were measured with specific RIAs in tumor tissue, in cell culture medium, and in plasma of Ewing sarcoma patients before and after chemotherapy as well as after tumor recurrence.Results: CCK mRNA was identified in 12 Ewing sarcoma biopsies sampled in two series and in four Ewing sarcoma cell lines but not in unrelated neoplasia. Immunoreactive proCCK was identified in the culturing medium of all Ewing sarcoma cell lines but not in the media from unrelated tumor cell lines. Moreover, in plasma from Ewing sarcoma patients, precursors and mature forms of CCK, in particular proCCK, were detected; several fold elevation of the total proCCK product was found in plasma from patients before treatment and after tumor recurrence, whereas successful chemotherapy reduced proCCK to basal concentrations. Plasma concentrations of proCCK paralleled the respective tumor size.Conclusions: This is the first study that consistently documents an altered CCK metabolism in human cancer; Ewing sarcomas synthesize and secrete proCCK that can be identified in plasma as circulating tumor marker.

Processing-Independent Quantitation of Chromogranin A in Plasma from Patients with Neuroendocrine Tumors and Small-Cell Lung Carcinomas

“…These results are in accordance with reports that PIA analyses have increased the diagnostic accuracy for progastrin (6,10 ), probrain natriuretic peptide, and rat epidermal growth factor (11,24 ). Furthermore, a PIA for procholecystokinin has recently been found to be a valuable tool for the diagnosis and monitoring of the efficiency of chemotherapy for patients with Ewing sarcomas, and the PIA proved superior to a conventional cholecystokinin RIA (14 ). An application of PIA for human CgA has not previously been published.…”

Cell-Specific Precursor Processing

“…In contrast, PIA did not improve the diagnostic sensitivity significantly for gastrinoma patients with consistently enhanced concentrations of carboxyamidated gastrin in plasma (Jørgensen et al 1998). For both proCCK progastrin and chromogranin A we could, however, show that PIA provides a significantly more accurate measure of the tumor burden for each individual patient than conventional RIA measurements (Bardram 1990;Børglum et al 2007;Reubi et al 2004). …”

“…These cancers include, for instance, all the major gastrointestinal carcinomas (colorectal, gastric, esophageal, pancreatic) as well as all forms of lung cancer and ovarial cancer (for review, see Rehfeld and van Solinge 1994). Even sarcomas express genes of peptide hormones at the proprotein level (Reubi et al 2004;Friedman et al 1992).…”

“…Therefore, only a smaller fraction of the precursors mature to bioactive products, and the sick cells consequently release mainly unprocessed and partly processed precursors (Jensen et al 1989). In malignant cells the capacity for maturation is sometimes so reduced that only inactive prohormones and processing intermediates are released from the cells van Solinge et al 1993a, b;Bardram 1990;Reubi et al 2004). The second type of deviation is simply due to lack of expression of appropriate processing enzymes, so that the cells produce only the intact prohormone, as seen in, for instance, Ewing's sarcoma which releases only proCCK to circulation (Reubi et al 2004).…”

The uncovering and characterization of a CCKoma syndrome in enteropancreatic neuroendocrine tumor patients

“…[5][6][7][8][9] Accordingly, it was suggested years ago that patients with a significant hyperCCKemia may have 'persistent gallbladder contraction, diarrhea, gastric acid hypersecretion with ensuing duodenal ulcers, anorexia, and perhaps anxiety'. [10] So far, tumor expression of CCK has been found only in pituitary corticotrophic tumors, [11] a few other neuroendocrine tumors, [12,13] Ewing sarcomas, [14] and gliomas, [15] but never to an extent where increased concentrations of CCK in plasma or symptoms thereof have been observed.…”